In Witcher 2 Assassins of Kings Enhanced Edition, Suspect: Thorak side-quest can be completed after you finish the Royal Blood main-quest, featured in the second act of the video game, if you sided with Iorveth.
If you finished Baltimore’s Nightmare and saved Stennis at the end of Royal Blood, it is time to finish Suspect: Thorak.
“After talking to the creator of the goblet which had been a gift from the folk of Vergen to Saskia Geralt decided to visit Thorak.
He suspected that the original goblet had been replaced with another, containing the poison. Thorak was the only artisan in Vergen capable of replication the original and thus producing the goblet use to poison the Dragonslayer.”
When to start
After Baltimores Nightmare and Royal Blood
Suspect: Thorak is a short quest and can be completed almost immediately. While tracking the quest, head to the north-eastern area of Vergen and check Thoraks mansion.
If you followed our Witcher 2 Assassins of Kings Enhanced Edition walkthrough and completed Baltimores Nightmare, you already know who Thorak is and where you can find his house.
After you find it, enter, and to the right, next to the entrance, you should see a weapon stand. Behind it, is a bookshelf and on it, a small chest.
Loot the chest using the key you have found in the dwarfs pockets (if you killed him), and you will complete the quest as well as The Walls Have Ears.